Process for forming bottomed tubular members from metal blanks

ABSTRACT

METAL BLANKS ARE PUNCHED INTO A STEPPED PRELIMINARY FORM HAVING A CIRCULAR CROSS-SECTION. DURING THE PUNCHING OPERATION, METAL FLOWS BOTH RADIALLY AND LONGITUDINALLY. THE PRELIMINARY FORM IS THEN SUBJECTED TO ANOTHER PUNCHING OPERATION EFFECTING A FURTHER FLOW OF METAL IN BOTH A RADIAL AND LONGITUDINAL DIRECTION THEREBY PRODUCING THE FINAL SHAPE OF THE BOTTOMED TUBULAR MEMBERS. DURING BOTH PUNCHING OPERATIONS, THE LONGITUDINAL FLOW   OF METAL IS IN A DIRECTION OPPOSITE TO THE MOVEMENT OF THE PUNCH.

Feb; 9; 1971 v O-BIIGINELLI 3,561,242

PROCESS FOR FORMING BOTTOMED TUBULAR MEMBERS FROM METAL BLANKS Filed Nov. .20. 19767 3 Sheets-Sheet 1 Feb. 9, 1971" i O. BYIGINELLII 3,561,242

PROCESS FOR FORMING BOTTOMED TUBULAR MEMBERS FROM METAL BLANKS Filed Nov. .20, 19 67 3 Sheets-Sheet z Feb.9, 1911 I QBIGI ELLi' 3,561,242

rRocEss FOR ORMIN BOTTOMED TUBULAR MEMBERS FROM METAL BLANKS Filed Nov. .20, 1967 I I v 3 Sheets-Sheet s United States Patent 3,561,242 PROCESS FOR FORMING BOTTOMED TUBULAR MEMBERS FROM METAL BLANKS Oreste Biginelli, Rue Buffon, Clermont Ferrand, Puy de Dome, France Filed Nov. 20, 1967, Ser. No. 684,300 Claims priority, appliclzizoglslirance, May 12, 1967,

Int. Cl. B21c 23/00 US. Cl. 72-256 4 Claims ABSTRACT OF THE DISCLOSURE There exists already a method of obtaining tubular elements, such as goblets, consisting of a drawing out operation in which a punch having the final shape and volume of the goblets to be produced penetrates into a block of metal placed in a die. The shape and volume of the die corresponds to that of the outside walls of the goblet.

The above mentioned process produces thin tubular elements with bottoms, but incurs serious inconveniences such as the rapid depreciation of the qualities of the extruding punch.

In effect, the temperature of the block to be extruded must be increased to between 950 C. and 1100 C. de pending upon the type of material, particularly because of the thin tubular elements being manufactured in strongly allied metals.

This process of extruding a thin tubular element in one single operation retains the contact between the extruding punch and the high temperature metal block for a relatively long period, thus incurring deterioration of the punch.

On the other hand, considering that the shape of the punch alfects the final shape of the internal profile of the desired goblet, this punch has a surface which is a little smaller than the diameter of the block of metal contained in the walls of the die. Thus, a very strong force, in the region of several hundred tons, must be exerted on the punch in order to draw out the block of metal between the punch and the walls of the die.

The combination of high temperature and pressure results in the rapid deterioration of the extruding equipment which is usually quite expensive.

The forming operation is often carried out in two parts. In the first operation, a punch having a diameter relatively small in relation to the diameter of the metal block contained in the walls of the die is used, and then the desired thickness of goblet is obtained by means of a larger diameter punch.

Following this process each operation entails extruding; in both of the operations the outer surface of the punch remains in contact with the metal block at high temperature and under a heavy pressure for an excessively long period. Even though the time is less than in the first example the deterioration of the punch working under such conditions of pressure and temperature takes place rapidly.

This invention is intended mainly to overcome these inconveniences; it deals with, in effect, a process for the hot forming of tubular elements with steel bottoms, which are manufactured in high resistance steel, comprising a metal block which is shaped by means of a hydraulic ex truding press. The process consists of submitting a metal block at low temperature to an initial deformation by subjecting it to an axial force by means of a punch having a penetrating head, thus obtaining a rough hollow form which is consequently submitted to a second operation at a low temperature and pressure consisting of introducing the form between a punch having the final desired shape and the walls of the die where it undergoes a simple deformation. This allows the reduction of the pressure and also the temperature necessary for the deformation of the tubular element. It also simplifies the final shaping of the tubular element. This latter operation being particularly easy due to the deformable pattern obtained in the first part of the operation.

Following another characteristic of the invention, the initial deformation of the metal block to be treated, consists of increasing the block volume so that its diameter is smaller than the largest diameter of the die, by penetration of the punch head into block. The punch head is made up of one or several cones preferably having steep angles.

Following another characteristic of the invention the initial deformation of the metal block to be formed consists of partly increasing the metal block whose diameter is equal to the largest diameter of the die by forcing the block into the smaller diameter section of the die by means of the punch then by forcing the head of the punch into the block to obtain a rough hollow.

Other purposes and advantages are born out by the following description, claims and accompanying sketches in which:

FIG. 1 is a sectional view of the working elements of the press, showing the primary stage of the first operation;

FIG. 2 is a sectional view showing the shaping of the hollow section in the second stage of the first operation;

FIG. 3 is a sectional view, showing the first stage of the second operation leading eventually to the final shape of the tubular element;

FIG. 4 is a sectional view showing the last stage of the last operation which results in the finished shape of the tubular element with its bottom section;

FIG. 5 is a sectional view showing an alternative method of carrying out the process concerned.

In accordance with the invention, the purpose is to obtain the hot forming of tubular elements with bottoms which are manufactured in metal, particularly high resistance steels, such as alloys or refractory steel.

Another purpose of the invention is to obtain the forming of the tubular elements with considerable reduction of the press tool wear, i.e. the punch and die, by reducing appreciably the temperature and pressure necessary for the forming of the tubular elements and their bottoms.

Following the invention, and in accordance with FIGS. 1 and 5, the forming of the tubular elements is obtained by use of a substantially cylindrical metal blank or block 1 which is extruded by means of a hydraulic press comprising a punch tool 2 and a die 3 which has a lower section 4 to give the final shape.

In each of the fabrication methods indicated in FIGS. 1 and 5 the metal blocks are submitted to an initial forming process, by applying an axial force by means of the penetrating head of the punch tool 2 to the block 1 to obtain a preliminary form having a rough hollow section 1 as indicated in FIG. 1. This rough form may then be further formed at low pressure and temperature to produce the final shape as is shown in FIGS. 3 and 4.

In the method of fabrication shown in FIG. 1, the forming of block 1 consists of deforming by means of extruding the block to obtain the preliminary form having the rough hollow section 1 FIG. 2.

In this case the diameter of the metal block 1 is less than the greatest diameter 3 of the die and the metal block is guided to the bottom of the die so that there exists a free space 6 between the largest part of the metal block length not contained in the largest diameter section of the die 3.

Due to this arrangement, the pressure exerted by the penetrating head of the punch tool 2 will bring about an enlargement of the metal block in both a radial and longitudinal direction to form the preliminary form having the hollow section 1 as indicated in FIG. 2. This shows the completion of the second phase of the first operation. It should be noted that the preliminary form has a stepped configuration which corresponds to the shape of the die and punch. As seen in FIG. 2 the preliminary form has a circular cross-section which converges along a major portion of the length from the open end to the closed, bottom end. The preliminary form has a stepped exterior portion which conforms to the shape of the die 3 and a conically stepped interior portion which conforms to the step punch head 5.

The pressure punch 2 and the penetrating point present a conical contact surface 5 preferably at a sharp angle which may be a replaceable wear piece. The penetrating point or head is removably mounted at the tip portion of the punch.

This piece may be, for example, manufactured in tungsten carbide or in high speed steel.

The penetrating head of the punch tool as shown, is complete with two cylindrical and concentric portions 5 and 5 which are parallel to the axes 7 of the punch 2. The surfaces of the portions are joined to each other by the conical sections 5 The two portions 5 and 5 serve as intervening portions and separate the concentric portions 5, and 5 The principal surface 5 of the punch tool decides the thickness of the hollowed out section 1 and corresponds to the diameter of the punch tool 8 which is used in the second stage of the process, FIGS. 3 and 4, and which produces the final shape of the tubular element. As can be seen in FIG. 2, the first stage deforming operation causes the metal blank to simultaneously deform in both its radial and longitudinal directions to form the preliminary form. Likewise, in the second stage deforming operation, the preliminary form is simultaneously deformed in both the radial and longitudinal directions to produce the completed bottomed tubular member.

The metal flow in the longitudinal direction is opposite to the direction of travel of the two punches 5 and 8 during both punching operations. Also, the punch 8 is provided with a peripheral edge portion (not numbered) adjacent and around the front face portion and as seen in FIG. 3, this peripheral edge portion is the only portion of the punch which contacts the preliminary form at the start of the second punching operation.

Equally in this process the greatest diameter 3 of the initial forming die 3 corresponds to the diameter of the die 9 responsible for the final shape of the tubular element 13.

Thus the smallest diameter of the hollowed out section forms a free space 10 between it and the wall of the final die in such a fashion that, following the final thrust of the punch tool 8, the walls of the hollowed section 1 merge with the outline of the die 9 giving the required shape. As seen in FIG. 4, the final bottomed tubular member has a uniform cross-section along substantially its entire length.

Following the method of fabrication indicated in FIG. 5 the initial forming of the block 1 consists of partly restraining the said metal block having a diameter equal to the greatest diameter 3 of the die so that being submitted to the force of the press tool 2 by means of the penetrating head 5 the block partially enters the small diameter section of the die 3 The head of the punch tool then penetrates into the block 1 to form a rough hollow which consequently undergoes under weak pressure the other operations producing the final tubular element.

The process dealt with by the invention produces numerous advantages, notably the following:

The metal tubular element complete with its bottom shape is produced in an exceptionally short period considering the short time necessary to obtain the preliminary hollowed out section and that of the finished shape.

On the other hand the initial forming of the highly alloyed steel may be done at a temperature in the region of 700 to 750 C, using a relatively low pressure press. The form thus obtained is given its final shape directly by means of a second press using the finishing tool, without the necessity of reheating the piece.

What we claim is:

1. A process for manufacturing a bottomed tubular member from a metal blank comprising: providing a substantially cylindrical metal blank to be worked on; punching said metal blank to effect deformation thereof simultaneously in both a radial and longitudinal direction into a preliminary form having a circular cross-section converged from one end thereof along a major portion of the length to the other end thereby defining a hollowed out interior portion; and then additionally punching said prelimiary form with a punch having a front face and a peripheral edge portion around said front face, said front face entering said hollowed out interior portion to contact said preliminary form only along said peripheral edge portion at the start of said additional punching, to effect deformation of said preliminary form simultaneously in both a radial and longitudinal direction into a bottomed tubular member having a uniform cross-section along substantially the entire length thereof.

2. A process according to claim 1; further including heating said metal blank to a temperature of between 700 to 750 C. prior to the first-mentioned deforming step; and maintaining the heated metal blank within said temperature range during said first-mentioned deforming step.

3. A process according to claim 2; further including performing the additional deforming step without externally heating said preliminary form.

4. A process according to claim 1; wherein the firstmentioned deforming step comprises punching said metal blank into a preliminary form having a stepped exterior portion and a conically stepped interior portion.

References Cited UNITED STATES PATENTS 2,748,932 6/1956 Kaul 72267 2,874,460 2/1959 Riethmiiller 72256X 1,996,335 4/1935 Jones 72273 2,930,483 3/1960 Kaul 72256X 2,184,048 12/1939 Krause 72273 FOREIGN PATENTS 312,571 5/1929 Great Britain. 595,633 4/1934 Germany.

CHARLES W. LANHAM, Primary Examiner A. L. HAVIS, Assistant Examiner US. Cl. X.R. 72267, 356 

